Pyelonephritis, illustration. Pyelonephritis refers to inflammation of the renal tissues including the calyces and the pelvis. In this case, the pathology is due to tuberculous infection resulting in a markedly enlarged pelvis extending into the renal pyramids and ureter. The cavernous dilations show many tuberculous nodules with cheese-like exudates of greyish-yellow fluid. This infection reaches the kidney via ascent of the urinary tract and if chronic leads to end-stage renal failure. From Bollinger, O. 1901 Atlas und Gundriss der Pathologischen Anatomie, vol 2. Lehmann, Munich.